Problem: Solve for $n$ : $9 = 29 + n$
Explanation: Subtract $29$ from both sides: $ \begin{eqnarray} \\ \hphantom{9 {- 29}} &\hphantom{=}& \hphantom{n} \\ 9 &=& 29 + n \\ \\ {-29} && {-29} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ 9 {- 29} &=& n \\ \end{eqnarray} $ Simplify. $ n = -20$